"Michael Lawford" wrote in message ...
Here is a query - I have heard that you can kill fish by overfeeding. I
never overfeed and my fish (who get fed different things about 3 times a
day) are always hungry when I feed them. Now here is the thing - in the
wild they can eat all day if they like - so why dont all marine fish die
from over eating? Especially the Regal Tangs - they are like vacuums and
eat everything you put in the tank!

Any comments?

You are doing a mistake treating all fish as a one thing...
There are many different kind of fish with different diets
and totally different demand on food or eating frequency...

Lets say predatory, carnivorous fish like eels, morays,
groupers - these fish eat a large prey but not frequently.

Consider planktivorous fish - eating plankton particles from
the water column. This is majority of fish on the reef...
These fish eat all day very tiny particles of small density
food. Each planktonic animal consist mostly of water (80%?)
and fish needs to eat millions of them to support itself...

And there are grazers like tangs - they mow the rocks of
algae. Similar situation with them: they eat all day very
small quantities of food totaling to a big meal over 12 hours.

In captivity - there is totally different situation...
First - your fish tank does not have constant supply of
plankton. Usually does not have constant supply of
macro-algae for tangs (outside of hair algae outbreaks,
but not all tangs even like to eat derbresia algae).
If you feed your fish with highly concentrated foods
like frozen/flake "Formula 1" each food particle has
much more nutrients, per weight, than the food fish
eat in the nature... Protein, fat content is close to
80%, instead of 10-15% for natural plankton...
If you feed your fish with Formula 1 food frequently
you are risking overfeeding and overfouling water with
nutrients... Same stands for dried seaweed. It is highly
concentrated, with almost no water content food...
I would use these foods in VERY small quantities through
the day spread over 3-4 feedings per day...

Other situation is with frozen food like whole organisms.
I am talking about things like frozen plankton, frozen
krill etc. Not processed food, just caught in the ocean
and frozen in the natural form... This is totally different.
The water content in such food is high, close to the content
in the natural food fish eat. Using this kind of food you
risk less with overfeeding because planktivorous fish appetite
is adjusted to this kind of food exactly... You can use this
food frequently over the day simulating natural conditions.

Consider also one important thing... Fish digestive systems
are not developed as well as digestive systems of mammals...
What the fish poops is not very processed food. Fish can
use very little from the food it eats... If you do not have
very good reef food chain of animals taking care of fish poop
(worms in the sand, snails, crabs and other "cleaning crew")
you will have a lot of problems with water quality if you
feed your fish properly... Of course you can do what most
aquarists do: starve the fish for the prolonged periods...
Keeping typical grazer fish like tangs or planktivorous guys
like clowns and feeding them every three-four days is cruel.
This kind of regime you can use to predatory fish like eels only!